'Views' to aggregate multiple categories (3 posts)

This seems so simple, I keep thinking something must exist, but none of my searches have turned up anything.

I'd like to set up simple ways for my reader to aggregate multiple categories that are of interest to them, or if you prefer to systematically exclude certain categories not of interest. E.g., I blog about poker, politics, and tech. Suppose a user wants to read about poker and politics but not tech, or tech and politics but not poker. The simple heirarchical categories, though a start, don't quite let me do this.

Is there such a plugin? If not, I'm probably going to code it myself; any pointers? (WP's source looks like an absolute rat's nest of poorly planned PHP.)

Due diligence: I searched "multiple categories", views and didn't find anything. Maybe I just don't know the search syntax.